coordination, and optimal Pd–N and Pd–C bond lengths.
The metal coordination environment of 13a is quite similar
to a previously characterized palladium(II) azuliporphyrin,
although the 1.946(5) A Pd–C distance is slightly shorter than
the 1.980(3) A value for the earlier example.20
In conclusion, the first fully conjugated porphyrinoid systems
with pyrazole subunits have been synthesized and the nature of
the N-substituent has been shown to be crucial for the stabiliza-
tion of this species. In addition, these diazacarbaporphyrinoids
readily form stable organometallic derivatives and in this
respect parallel the properties of the N-confused porphyrins.
This work was supported by the National Science Founda-
tion under Grant Nos. CHE-0616555 (to T. D. L.) and
CHE-0348158 (to G. M. F.), and the Petroleum Research
Fund, administered by the American Chemical Society. The
authors also thank Youngstown State University’s Matthias
Zeller for X-ray data collection.
Scheme 2 Metalation of pyrazole-containing NCP analogues.
Notes and references
z Crystal data 13a: C35H35N5Pd,
M = 632.08, monoclinic,
a = 11.922(2), b = 16.776(3), c = 14.465(3) A, b = 102.546(3)1,
U = 2824.0(9) A, T = 100 K, space group P21/n (no. 14), Z = 4,
27 503 reflections measured, 8558 unique (Rint = 0.100), R1 = 0.0721
[I 4 2s(I)], wR2 = 0.1397 (all data).w
1 (a) H. Furuta, T. Asano and T. Ogawa, J. Am. Chem. Soc., 1994,
116, 767; (b) P. J. Chmielewski, L. Latos-Grazynski, K. Rachlewicz
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2 G. R. Geier, III, D. M. Haynes and J. S. Lindsey, Org. Lett., 1999,
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3 For rational syntheses of meso-unsubstituted NCPs, see:
(a) B. Y. Liu, C. Bruckner and D. Dolphin, Chem. Commun.,
1996, 2141; (b) T. D. Lash, D. T. Richter and C. M. Shiner, J. Org.
Chem., 1999, 64, 7973.
Fig. 3 ORTEP III drawing (50% probability level, hydrogen atoms
drawn arbitrarily small) of compound 13a. Selected bond lengths (A):
C(1)–N(2) 1.384(6), N(2)–N(3) 1.344(5), N(3)–C(4) 1.377(6),
C(4)–C(21) 1.405(6), C(21)–C(1) 1.383(6), Pd–C(21) 1.946(5),
Pd–N(22) 2.018(4), Pd–N(23) 2.038(4), Pd–N(24) 2.011(4). Selected
bond angles (1): C(1)–N(2)–N(3) 111.5(4), N(2)–N(3)–C(4) 104.3(4),
N(3)–C(4)–C(21) 112.3(4), C(4)–C(21)–C(1) 103.7(4), C(21)–C(1)–N(2)
108.2(4), C(21)–Pd–N(22) 88.9(2), C(21)–Pd–N(23) 179.9 (2),
C(21)–Pd–N(24) 89.4(2), N(22)–Pd–N(24) 178.1(2).
¨
4 J. L. Sessler and S. Weghorn, Expanded, Contracted
Isomeric Porphyrins, Pergamon, New York, 1997.
&
5 L. Latos-Grazynski, in The Porphyrin Handbook, ed.
K. M. Kadish, K. M. Smith and R. Guilard, Academic Press,
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6 A. Srinivasan and H. Furuta, Acc. Chem. Res., 2005, 38, 10.
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8 H. Furuta, T. Ishizuka, A. Osuka, H. Dejima, H. Nakagawa and
Y. Ishikawa, J. Am. Chem. Soc., 2001, 123, 6207.
9 (a) Unpublished results on the synthesis of pyrazole-containing
hexaphyrin-like systems by E. Lind and E. LeGoff are described in
ref. 4, pp. 364–366; (b) E. Lind, MS Thesis, Michigan State
University, 1987.
6.18–6.63 ppm. The associated shifts to the substituents were
consistent with the formation of a nonaromatic species and the
pyrrolic methyls shifted upfield by 0.4–0.6 ppm. These results
are to be expected if the aromatic characteristics of the
nonprotonated metallo-derivatives derive from the electron-
donating pyrazole (i.e., from contributors 14) because the
protonated species would have to place two positive charges
directly next to one another if this type of interaction still
played a role.
10 (a) S. Katsiaouni, S. Dechert, C. Bruckner and F. Meyer, Chem.
¨
Commun., 2007, 951; (b) S. Katsiaouni, S. Dechert, R. P. Brinas,
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¨
11 T. D. Lash, Chem.–Eur. J., 1996, 2, 1197.
12 T. D. Lash, in The Porphyrin Handbook, ed. K. M. Kadish,
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13 (a) T. D. Lash, Synlett, 2000, 279; (b) T. D. Lash, Eur. J. Org.
Chem., 2007, 5461.
The X-ray crystal structure of palladium complex 13b has
also been obtained (Fig. 3),z and this not only confirms the
presence of a ‘‘confused’’ pyrazole but also demonstrates that
the macrocycle is quite planar as evidenced by the 0.073 A rms
distance the framework atoms lie from the plane defined by
C(21), N(22), N(23), and N(24). In fact, only N(3) (0.1541 A),
C5 (0.1715 A), and C7 (0.1787 A) deviate more than 0.15 A
and 18 of the 25 framework atoms deviate less than 0.03 A
from this plane. The structure exhibits framework bond dis-
tances consistent with a generally localized p-bonding model,
so the planarity is primarily dictated by constraints of palla-
dium atom binding, namely the Pd(II) size, square-planar
14 R. Bohme and E. Breitmaier, Synthesis, 1999, 2096.
¨
15 (a) Unpublished results on the synthesis of 2,3-diazaporphyrins by
M. L. Waldo and E. LeGoff are described in ref. 12, pp. 186–187;
(b) M. L. Waldo, MS Thesis, Michigan State University, 1999.
16 S. Kai, M. Suzuki and Y. Masaki, Tetrahedron Lett., 1998, 39,
4063.
17 W. Jaio, MS Thesis, Illinois State University, 1999.
18 D. T. Richter and T. D. Lash, Tetrahedron Lett., 1999, 40, 6735.
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20 T. D. Lash, D. A. Colby, S. R. Graham, G. M. Ferrence and
L. F. Szczepura, Inorg. Chem., 2003, 42, 7326–7338.
ꢀc
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